In general, car manufacturers have three different reasons to perform crash tests: (1) meeting US and European regulations in order to get the official approval and homologation for road service in the various countries; (2) meeting the requirements of various consumer tests such as EuroNCAP, US-NCAP, JNCAP etc.; and (3) research and development tests that give the design engineers valuable inputs to create safer cars. The National Highway Traffic Safety Administration (NHTSA) has a legislative mandate under Title 49 of the United States Code, Chapter 301, Motor Vehicle Standard, to issue Federal Motor Vehicle Safety Standards (FMVSS) and Regulations to which manufacturers of motor vehicles and items of motor vehicle equipment must conform and certify compliance. Part 572 defines the Anthropomorphic Test Devices.
Included in these regulations are definitions for the Hybrid III 50th male, 5th female, 3-month-old, 9-month-old, 6-year-old, and 9-year-old frontal impact dummies, and a 50th male side impact dummy. Several new frontal and side impact dummies are currently being reviewed world-wide for inclusion in enhanced safety standards. FMVSS 208 and 209 define testing methods for frontal impact tests, and FMVSS 214 defines methods for side impact crash tests. Similar standards exist throughout the world.
See Procedures for Assembly, Disassembly, and Inspection (PADI) of the Hybrid III 5th Percentile Adult Female Crash Test Dummy (HIII-5F0, Alpha Version revised June 2002, National Highway Traffic Safety Administration (NHTSA reference), which is incorporated by reference in its entirety.
The regulations also define standards for impact protection based on a variety of force, acceleration, and displacement measurements taken on the dummies during a crash. Of particular importance is measurement of the deformation of the ribs of crash test dummies. FIG. 13 shows a side view of a Hybrid III 5th female ATD, and FIGS. 14A and 14B show front and side views of the chest of the Hybrid III 5th female, all taken from the Hybrid III NHTSA reference. The construction of this dummy is representative of the Hybrid III series.
The Hybrid III 5th female ATD comprises a head assembly 1201, a neck assembly 1203, an upper neck bracket 1205, a lower neck bracket 1207, an upper rib guide 1209, an upper torso assembly 1211, a lower rib guide 1213, a lower torso assembly 1215, and a leg assembly 1217. FIGS. 14A and 14B provide a closer view of upper torso assembly 1211, which is where measurements of the deformation of the ribs are performed. Torso assembly 1211 comprises a rib set 1301 held in place with the use of behind rib straps 1303 and stiffener strip 1305, all contained within bib assembly 1307.
Currently, a potentiometer and linkage 1315 is used to measure the compression of the sternum 1311 towards the spine, or sternum stop 1309, at a single point in the middle of the sternum. Chest transducer assembly 1313 receives data from the potentiometer and linkage assembly 1315 and aids in the computation of chest deflection. One end of the linkage has a ball that rides in a track on the front of the sternum. Under severe impacts the ball disconnects from the track, invalidating the data collected. Automotive safety experts wish to get motion data from multiple points on the chest, and to extend the measurements from a single axis to two or three axes.
Alternatives to the chest potentiometer have been built and are currently being evaluated, including the “Thumper” which measures compression at 4 points on the chest, and a multipoint linkage system that measures three degrees of freedom at 4 points on the chest, such as the THOR Advanced Crash Test Dummy. They have not been incorporated into regulations at this time.
See THOR Advanced Crash Test Dummy User's Manual of the 50th Percentile Male (Alpha Version 1.1 released Dec. 14, 2001, National Highway Traffic Safety Administration reference), which is incorporated by reference in its entirety.
FIG. 1 shows a side view of a THOR (Test Device for Human Occupant Restraint) Alpha 50th male version ATD, taken from the THOR Advanced Crash Test Dummy NHTSA reference. The ATD 100 comprises an instrumented head and face 101, a neck assembly 103, shoulder assembly 107, neck pitch change mechanism 109, adjustable posture spine assembly 111, pelvic assembly 113, femur assembly 115, instrumented abdominal assembles 119, and lower leg assembly 121. ATD 100 provides an estimate of bodily harm or deformation of the rib area of a human male with the use of elliptical ribs 105 and a four point chest deflection instrumentation 117.
A more detailed view of the elliptical ribs 105 and four point chest deflection instrumentation 117, may be seen in FIGS. 2A and 2B, taken from the THOR Advanced Crash Test Dummy NHTSA reference. Torso 117 comprises a rib assembly with rib stiffeners 201, a thoracic spine load cell 203, upper compact rotary units (CRUX) 205, lower CRUX units 207, a triaxial accelerometer 209, a sternal plate comprising a uniaxial accelerometer 211, an upper sternum 213, and a protective bib covering 215.
The triaxial accelerometer 209 is located in the center of gravity of torso 117 and is used to measure acceleration along three principle axes. The uniaxial accelerometer 211 is positioned on the sternal plate is and is used to measure acceleration at that point.
The upper and lower CRUX units, 205 and 207 respectively, measure the deflection of the rib cage and capture three dimension deformation data. The CRUX units comprise a two bar linkage system which features three measured degrees of freedom to provide a three-dimensional measurement. The CRUX unit comprises an end joint 224 with rotary capability, a mid joint 226 and a base joint 228. The mid joint 226 and base joint 228 further comprise precision rotary potentiometers 230 to measure the position of the various link-arms. A single potentiometer is mounted at the mid-joint and two potentiometers are mounted at the base joint. The CRUX unit is attached to the sternum bib through a bib attachment 222.
During impact testing, the output voltages from each of the three potentiometers are recorded with data acquisition systems. This data is processed to convert the output voltages into three-dimensional coordinates for X, Y, and Z displacement. Therefore the initial, dynamic and final positions of the unit may be determined directly from the potentiometer output voltage signals.
A tube lighting technique has also been developed where light emitting diodes and sensors are placed on opposite sides of an ATD rib connected by a telescoping tube. The telescoping tube will contract once the ribs are comprised. The light measured by the sensors will be increased in intensity once the ribs are comprised. A measurement of rib deformation may be achieved by measuring the intensity changes of the light.